Caged core structure

Fig. 3.5-12. Core structures of GagOgMesg 48 and the dodecagallium cage 49 (Bu groups are omitted, and the bridging O atoms and OH groups of 49 are disordered).

The material reviewed in this Chapter hitherto has focused on metallacarboranes in which the metal atom is a vertex in an icosahedral cage framework. Until recently, monocarbollide metal compounds with core structures other than 12 vertexes were very rare since suitable carborane precursors were not readily available." However, Brellochs recent development of the reaction of decaborane with aldehydes to give 10-vertex monocarboranes permits a considerable expansion in this area of boron cluster chemistry. As a consequence, several intermediate-sized monocarboranes are now easily accessible and we have recently begun to exploit the opportunities that these present. In particular, we have focused thus far on complexes derived from the C-phenyl-substituted species [6-Ph- zJo-6-CBgHii] It is clear from these initial studies that a wealth of new chemistry remains to be discovered in this area, not only from among the metal derivatives of PhCBg car-boranes such as those discussed in this section, but also in the metal complexes of other newly available carboranes. 

Figure 2 Core structures for orgaaomunoalaaes with nitrogen and aluminiun atoms alternating at cage vertices. Organic snbstitnents R and R are omitted for clarity...

The structure of complex 20, outlined in Fig. 5, consists of a cubane-like, 72-electrons M4E4 cage core, which is unprecedented for ruthenium and selenium. Also this complex should be regarded as a secondary product, probably formed by the self-assembly of two dinuclear Ru2Sc2 groups, derived from 18 (Ru3Se2) by loss of a mononuclear metal fragment. 

Complexes 104, the FeCp"(CO)2 analogs of 99 (Gp" = 1,3-BuVcyclopentadienyl), are prepared by reaction of Cp"(OC)2Fe Gl2 with Na2[Fe(CO)4]. The products from 104a and 104c are accompanied by formation of the hepta- 105 and pentanuclear cage cluster complexes 106 with weak E- E interactions, respectively. The core structure of the latter complex resembles that of 102,... 

POSS not only leads to self-assembling phenomena but also it has a strong effect on the chain mobility in polymers. POSS has a very low mobility in the polymer structures and therefore can be viewed as anchoring points linked to the macromolecules [70]. This effect is based not only on the rigid POSS core structure but also on the chemical structure of the organic ligands. Therefore different substitution patterns at the POSS cage can lead to variations in the macroscopic properties of the polymers. 

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